Electric power systems have multiple generation units that operate in synchronism under a normal operation. That is, frequency, phase, and amplitude of voltages at the terminals of a generator hold a fixed relationship with the same parameters of the remaining generators in the power system. Before a generator can be connected to an electric power system, the frequency, phase, and amplitude of the voltages at its bus need to be matched with those of the power system at the point of interconnection. Once, the so called synchronization parameters are matched within a desired tolerance, the generator breaker is closed. Any mismatch in the synchronization parameters during connection of a generation unit by a generator breaker may result in undesired transients and disruption of the system.
Traditional synchronization methods for two grid systems is calculating and adapting reference values of the governor and excitation systems. From the frequency deviation and phase angle difference points of view, the total synchronization time is largely depending on the primary and secondary controller of the generator. For a large scale generation system, synchronous machine based power generations, can take several minutes for the grid to finish the synchronization process. However, with the fast development of renewable energy generations, the entire gird is becoming more distributed. Due to the fact that the distributed grid is vulnerable than synchronous machine based grid system, the synchronization method purely relying on the primary and secondary controller is not feasible.
Therefore, the fast synchronization is desired to improve the robustness of the modern power systems. For example, U.S. Pat. No. 7,915,868 B1 disclosed a method of reducing the time to synchronize a turbomachine generator with the electrical grid system. The present disclosure is focused on the design of voltage synchronization during the start-up process of the synchronous machine, among other things. However, the phase and frequency synchronization is more critical than voltage synchronization and not addressed appropriately.
Therefore, there is a need to develop more effective way to achieve fast synchronization with the help of battery systems.